Mediator of RNA polymerase II transcription subunit 22 (IPR009332)

Family relationships

Description

The Mediator complex is a coactivator involved in the regulated transcription of nearly all RNA polymerase II-dependent genes. Mediator functions as a bridge to convey information from gene-specific regulatory proteins to the basal RNA polymerase II transcription machinery. The Mediator complex, having a compact conformation in its free form, is recruited to promoters by direct interactions with regulatory proteins and serves for the assembly of a functional preinitiation complex with RNA polymerase II and the general transcription factors. On recruitment the Mediator complex unfolds to an extended conformation and partially surrounds RNA polymerase II, specifically interacting with the unphosphorylated form of the C-terminal domain (CTD) of RNA polymerase II. The Mediator complex dissociates from the RNA polymerase II holoenzyme and stays at the promoter when transcriptional elongation begins.

The subunits form at least three structurally distinct submodules. The head and the middle modules interact directly with RNA polymerase II, whereas the elongated tail module interacts with gene-specific regulatory proteins. Mediator containing the CDK8 module is less active than Mediator lacking this module in supporting transcriptional activation.

Individual preparations of the Mediator complex lacking one or more distinct subunits have been variously termed ARC, CRSP, DRIP, PC2, SMCC and TRAP.

This entry represents subunit Med22 of the Mediator complex. It contains several eukaryotic Surfeit locus protein 5 (SURF5) sequences. The human Surfeit locus has been mapped on chromosome 9q34.1. The locus includes six tightly clustered housekeeping genes (Surf1-6), and the gene organisation is similar in human, mouse and chicken Surfeit loci [PMID: 11891058].